In general, in the washing machines, there are a pulsator type washing machine having an upright drum, and a drum type washing machine having a drum laid down horizontally.
Because the drum type washing machine has the horizontal drum, the drum type washing machine performs washing by dropping down laundry.
FIGS. 1 and 2 each illustrates a related art drum type washing machine, schematically.
That is, the drum type washing machine is provided with a body 10, a tub 20 in the body 10, a drum 30 rotatably mounted in the tub 20, and a driving unit for driving the drum 30.
The body 10 has an introduction opening 11 in a front for introduction of laundry, with a door 40 at an edge of the introduction opening 11 for opening/closing the same.
There are dampers 21 on opposite sides of a lower portion of an outside circumference of the tub 20, to support the tub 20.
There is a washing water heater 60 on a lower portion of an inside of the tub 20, for enabling control of a temperature of the washing water.
The drum 30 is rotatably mounted in the tub 20, and has a plurality of pass through holes 31 in a circumferential surface for free flow of water therethrough.
The washing water can be supplied to the tub 20 through a detergent box 50, for supplying detergent or bleaching agent, together with the washing water.
The driving unit is provided with a driving motor 71 for driving the drum 30, and a belt 72 for transmission of driving power from the driving motor 71 to the drum 30.
The related art drum type washing machine washes laundry, in general, by performing a washing cycle, a rinsing cycle, and a spinning cycle for a preset time period automatically in response to control signals from a controller (not shown) in a state the laundry and the detergent is introduced in the drum 30.
In the meantime, regardless of kinds, the washing machine has dirt from the laundry, and remains and mixtures of the detergent and softener stuck to an inside wall of inside/outside walls of the drum 30, and an inside wall of the tub 20, to cause re-contamination of the laundry during washing, to impair reliability of the washing machine in view of hygiene.
Moreover, bad odor is produced from microbes, such as fungus on the dirt when the washing tub (tub or drum) is contaminated, to drop reliability of the washing machine in view of sanitary, too.
Eventually, a washing tub washing course has been developed recently, for removing various kinds of contaminants on the inside/outside walls of the drum 30 or on the inside wall of the tub to prevent the re-contamination.
The washing tub washing course will be described, briefly.
Upon selection of the washing tub washing course as a time for performing the same is due, the controller makes to supply the washing water to a water level substantially the same with the washing cycle together with washing tub cleaning detergent
The drum 30 is kept rotating to perform the washing cycle.
According to this, the various kinds of contaminants is separated from the inside wall of the tub 20 or the inside/outside walls of the drum 30, to wash the tub or the drum, and as the washing water is drained, the separated contaminants are discharged from an outside of the washing machine.
When the draining is finished, new washing water containing no detergent is supplied to the tub 20, and, at the same time, the drum 30 is rotated, to perform the rinsing cycle.
Then, when the rinsing cycle is finished, the washing water is drained finally, and a spinning cycle is performed, to finish the washing tub washing course.
However, the related art washing tub washing course consumes an excessively large amount of the washing water, not only in the initial washing cycle, but also in the rinsing cycle, to result in waste of water and power, and in one aspect, the washing course is also not effective.
That is, the initial step of the washing tub washing course requires a large amount of washing water, because the dirt can be separated from the tub 20 or the drum 30 to a certain extent only when the drum is kept submerged in the washing water for a long time.
Moreover, since a temperature of the washing water is not high, the dirt can be separated smoothly only when the drum is kept submerged in the washing water for a long time. This long time submergence of the drum leads a time period required for the course substantially long.
Though the supply amount of the washing water can be reduced, if a condition for washing the tub 20 or the drum 30 is optimized by elevating an inside temperature of the drum adequately, in this case, because the heater (not shown) is required to generate heat for a long time for elevating the temperature inside of the drum, the case is not effective due to excessive power consumption.
In the meantime, if the washing tub washing is performed in a state the powder detergent is in the washing tub, the powder detergent produces much foam, to impede rotation of the washing tub, putting a load on the motor that rotates the washing tub, to cause a power loss at the end.
Moreover, the problems taken place in the related art method for washing a washing tub in a washing machine is not limited to the foregoing drum type washing machine, but applicable to the pulsator type washing machine having an upright drum, and to a washing machine only having a drum without the tub in the body as well as a washing machine having a tub and a drum in the tub.
The washing tub herein denotes a tub or a drum. That is, in a washing machine having both the tub and the drum, the washing tub herein denotes either the tub or the drum, or both the tub and the drum, and if the washing machine only has the drum without the tub, the washing tub herein denotes the drum.